Introduction: Lipid laden macrophages (LLM) are reported to be pathognomonic findings in exo- and endo-genous lipoid pneumonia [Allen, Clin Pediatr 1986; 25:541-545]. Several studies found LLM in lungs on autopsy of newborns receiving Intralipid® [Dahms, J.Pediatr 97:800, 1980]. Recalde et al.[Pediatr Pathol. 1984; 2:25-34] showed that LLM are present in tracheal aspirates of newborn infants on IV lipid infusions. Little is known about the usefulness of LLM as a marker of aspiration in neonates.Figure

figure 1

Figure 1

Purpose: To compare LLM indexes from tracheal aspirates of neonates with and without IV lipids.

Methods: All intubated infants who were not receiving gastric feedings were eligible for the study. Tracheal aspirates were obtained once daily and analyzed for LLM Index. [Corwin, Am Rev Respir Dis.1985;132:576-581]. Alveolar macrophages are graded 0-4 in direct relationship to the amount of lipid per cell. 100 consecutive macrophages are graded; maximal LLM Index = 400

Results: Of 91 samples from 20 babies, 16 were unsatisfactory due to insufficient quantity of material or technical problems. The mean value of LLM index from samples during Intralipid® infusion = 91.8 (SD=59.53), and from samples when no Intralipid® was infused = 24.81 (SD=39.55), p< 0.001.The LLM index from tracheal aspirate appears to rise into a low range after birth. With IV lipid infusion, the LLM index appears to rise to a higher level.

Conclusion: The Lipid Laden Macrophage Index is elevated during Intralipid® infusion. This may interfere with the use of LLM index as a marker of milk aspiration in neonates receiving IV lipids.